Lumbar Medial Branch Block

A lumbar medial branch block is a diagnostic procedure used to discover the origin of chronic back pain related to the lumbar area of the spinal column. It involves an injection of a local anesthetic near or around the medial branch nerves of the lumbar spine. These nerves exist in pairs on the posterior portion of the spinal column. Their only function is to carry pain signals from the area of the facet joint toward the brain. The facet joints are found between the vertebrae. These joints stabilize and allow for motion in the spine. Facet joint pain is the cause of around 45 percent of all back pain reported by patients.

Whenever a facet joint is irritated, inflamed, or damaged, it may lead to pain involving the buttocks, abdomen, low back, groin, or lower extremities. If a lumbar medial branch block does not decrease pain levels, the facet joint is most likely not the origin of back pain. If a lumbar medial branch block produces a dramatic decrease in pain levels, the facet joint is most likely the reason for the back pain. Hence, the block is indicated for diagnostic purposes, as opposed to therapeutic purposes, with regard to chronic low back pain. 

Although facet joint disorders are frequently the source of back pain, chronic pain can also be due to trauma or injury. Another common condition that can affect the facet joints is arthritis. It occurs when the cartilage that protects the joints or the synovial fluid that cushions them begins to degrade.

Arthritis is commonly due to aging but can also be due to an autoimmune condition. Facet joint arthritis, in particular, can cause spinal discomfort and pain. Chronic back pain can also be due to scoliosis, an abnormal curvature of the spine, and bad posture. Lumbar medial branch blocks are safe and helpful for treating back pain. This method is also advantageous because it is non-invasive and allows patients to avoid surgery.

Most patients who receive lumbar medial branch blocks have failed more conservative therapy including anti-inflammatories, analgesics, opioids, gabapentin, physical therapy (PT), or chiropractic manipulation.

Why Is A Lumbar Medial Branch Block Performed?

Conditions Treated With Lumbar Medial Branch Block

Medial branch blocks may help with the following pain conditions:

• Sacroiliac joint pain.
• Facet joint pain.
• Osteoarthritis.
• Spondylosis, or degenerative disc disease.
• Spinal stenosis, which is an abnormal narrowing of the spine.
• Failed back syndrome, aka post-laminectomy syndrome, that is defined by still having pain after back surgery.

However, lumbar medial branch blocks can also relieve sciatic pain so that additional treatment can address the underlying condition.

A lumbar medial branch obstruction can result in one of three outcomes:

As a diagnostic tool, if the injection does not relieve the pain, it indicates that the pain is most likely not coming from the targeted facet joints.

If the pain is gone for a few hours but returns and does not improve, it is likely due to the joints. The doctor learns, as a diagnostic tool, that the steroid medicine in the injection did not improve the pain.

If the pain goes away after the injection, returns, but then improves over the next few days, the steroid has a long-lasting effect on the pain.
If the injections give positive, long-term pain relief, the doctor can recommend three further injections in the same region within six months.

Pain Management:
Furthermore, lumbar medial branch block treatment typically helps patients regain at least 50% of their mobility, with more than 80% of patients regaining mobility by their two-year follow-up.

Medial branch blocks in the lumbar region significantly relieve lower back pain and assist around 40% of patients to regain mobility. Most patients also report a 50 percent reduction in pain after therapy.

Lumbar medial branch blocks are also good diagnostic techniques that assist physicians in determining the progression of some spinal conditions and whether or not a patient may require more intrusive interventions such as surgery.

How Is A Lumbar Medial Branch Block Performed?

The patient lies on their stomach on a table in the procedure room. The lower back is cleansed with an antiseptic solution and the injection area is marked with a felt-tipped surgical pen. The area is then infiltrated with a local anesthetic. Under fluoroscopic guidance, a thin procedure needle is inserted into the targeted medial branch nerve area and contrast dye may be injected to ensure that the anesthetic will flood the correct area near or around the nerves. Once proper direction of flow is established, the physician slowly injects an anesthetic and removes the needle. Sometimes, the anesthetic will be mixed with a steroid to prolong the effect of the anesthetic. 

A lumbar medial branch block is more targeted than a steroid injection, and the effects persist considerably longer. During the process, the nerves that give sensations to the facet joints (e.g., medial branch nerves) are the target. To block nerve signals, a needle is placed into the area containing the affected nerves, and then drugs that damage nerve tissue are injected.

Most patients report immediate relief of pain. If this is the case, the cause of pain is the facet joints. Any pain relief attributed to the injection is short-lived, and for this reason, the patient will be referred for another procedure, radiofrequency ablation (RFA). This procedure has the possibility to provide sustained pain relief in the case of facet-related back pain.

What To Expect After A Lumbar Medial Branch Block

It results in a semi-permanent interruption of pain signal transmission and considerable pain alleviation from facet joints. The risks associated with a medial branch block are due to needle placement issues or other technical faults. 

These issues are usually avoidable since the needle placement is guided by imaging instruments such as an ultrasound, X-ray, or fluoroscope. When imaging technology is used during the process, needle placement accuracy is around 90%. Other potential complications include bleeding at the injection site, nerve injury, and infection.

In addition to the drug that damages nerve tissue, steroids and an anesthetic are administered to the affected area. Weight gain and higher blood sugar levels are the possible side effects of steroids. Steroids can also impair the immune system and cause stomach ulcers.

The anesthetic may cause gradual desensitization of healthy nerves and undesired interactions with the medicine that the patient is taking. The injected anesthetic may cause nausea, chest discomfort, and temporary neurological issues in rare cases. It has only happened in about 2% of individuals who have undergone medial branch blocks. 

Because of the possibility of such consequences, physicians undertake medical examinations before determining whether or not a patient is a good candidate for a lumbar medial branch block.